This May Make Men Stay Faithful

Oxytocin has long been deemed “the love hormone,” after its important role in social bonding has been documented. But now, researchers have performed a new experiment that suggests oxytocin stimulates the reward center in the male brain, increasing partner attractiveness and strengthening monogamy.

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Oxytocin is the same chemical in the brain that’s responsible for helping infants bond to their mothers. But the hormone may also make men subconsciously view their female romantic partners as more attractive than women who are strangers—and that’s even if these unknown ladies were considered equally as good looking.

For the study, researchers tested 40 men. All had been in a relationship for at least six months and said they were passionately in love with their partners. Scientists watched these men’s brains on a scanner while they inhaled a nasal spray containing either oxytocin or a placebo. Then researchers instructed the men to view photographs of their partners and also strangers who had been previously matched as being “equally attractive.”

After watching numerous brain scans, researchers found that for those men who were given oxytocin, the pleasure and desire regions of their brain lit up intensely upon seeing their significant others. But when the men saw casual acquaintances or strangers, these areas either lit up far less or were not activated at all.

“Once men receive oxytocin, the attractiveness of the partner increases compared to the attractiveness value recorded for other females,” said Rene Hurlemann, MD, PhD, a professor of psychiatry at Germany’s University of Bonn, and the study’s lead author. In that way, the hormone creates unconscious biases that may indirectly cause a man to favor one woman above all others.

In the scientific community, oxytocin is known as the “cuddle chemical” because it is released in the brain when couples kiss and hug, as well as during orgasms and other intimate activities. Studies also show that the more of these moments a couple has, the more oxytocin is released and stored in the body.

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The research also backs up a previous study on oxytocin that showed men in long-term relationships who were given the hormone actually kept a greater physical distance from an attractive research associate as compared with single men.